Commander under Caliph Ali ibn Abi Talib during the Battles of the Camel (656) and Siffin (657). He opposed the truce with Muawiyah, ruler of Syria and a relative of Uthman, suspecting him of trying to sabotage Ali's impending victory in Siffin. Ali appointed him governor of several cities in Iraq and Syria, but this provoked opposition from Muawiyah. In 657 Ali appointed him governor of Egypt. En route to Egypt al-Ashtar was poisoned in al-Arish, apparently on orders from Muawiyah.
See also Siffin, Battle of